1. Field of the Invention
This invention relates to plastic optical articles having excellent properties such as heat resistance, abrasion resistance, transparency, and solvent resistance.
2. Description of the Related Art
Plastic materials in general are light in weight and have excellent impact resistance, processability, and mass-producibility, and therefore, the demand for the plastic materials for optical devices such as an optical filter, an optical lens and an optical disk has increased. Transparent resins such as poly(methyl methacrylate), polystyrene and polycarbonate are mainly used at present as the plastic material for these optical devices, but these materials have problems in that the thermoplastic resins not only have low heat resistance, as typified by a thermal deformation temperature, but also have low solvent resistance and a low elastic modulus.
In addition to the problems described above, the plastic optical devices have lower surface hardness than inorganic glass, and many attempts have been made to solve this problem. For example, there has been proposed a method by which an inorganic material such as SiO.sub.2 is deposited on the surface of a plastic substrate by vacuum deposition (Japanese Unexamined Patent Publication No. 58-204031), and a method by which a polyorganosilane type hard coat film or an acrylic type hard coat film is coated on the surface of the plastic substrate (U.S. Pat. Nos. 3,986,997 and 4,211,823 and Kokai (Japanese Unexamined Patent Publication Nos. 57-168922, 59-38262, 59-51908, 59-51954, 59-78240, 59-89368, 59-102964, 59-109528, 59-120663, 59-155437, 59-174629, 59-193969, 59-204669), and so forth.
The improvement of the surface hardness by vacuum deposition of the inorganic material such as SiO.sub.2, according to the prior art, can provide high hardness, but leads to critical problems such as lowered adhesion to the substrate, and lower heat resistance and light resistance. The technique described in Japanese Unexamined Patent Publication Nos. 59-38262, 59-51908, etc., by which a silane type and acrylic type hard coat film is coated, can improve the heat resistance to some extent, but the effect thereof is still unsatisfactory.